<literal>__getattr__</literal>)</term>
     <listitem>
      <para>
       This works the same as a mapping.
       Example:

<programlisting>
CREATE FUNCTION make_pair (name text, value integer)
  RETURNS named_value
AS $$
  class named_value:
    def __init__ (self, n, v):
      self.name = n
      self.value = v
  return named_value(name, value)

  # or simply
  class nv: pass
  nv.name = name
  nv.value = value
  return nv
$$ LANGUAGE plpython3u;
</programlisting>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

   <para>
    Functions with <literal>OUT</literal> parameters are also supported.  For example:
<programlisting>
CREATE FUNCTION multiout_simple(OUT i integer, OUT j integer) AS $$
return (1, 2)
$$ LANGUAGE plpython3u;

SELECT * FROM multiout_simple();
</programlisting>
   </para>

   <para>
    Output parameters of procedures are passed back the same way.  For example:
<programlisting>
CREATE PROCEDURE python_triple(INOUT a integer, INOUT b integer) AS $$
return (a * 3, b * 3)
$$ LANGUAGE plpython3u;

CALL python_triple(5, 10);
</programlisting>
   </para>
  </sect2>

  <sect2 id="plpython-data-set-returning-funcs">
   <title>Set-Returning Functions</title>
  <para>
   A <application>PL/Python</application> function can also return sets of
   scalar or composite types. There are several ways to achieve this because
   the returned object is internally turned into an iterator. The following
   examples assume we have composite type:

<programlisting>
CREATE TYPE greeting AS (
  how text,
  who text
);
</programlisting>

   A set result can be returned from a:

   <variablelist>
    <varlistentry>
     <term>Sequence type (tuple, list, set)</term>
     <listitem>
      <para>
<programlisting>
CREATE FUNCTION greet (how text)
  RETURNS SETOF greeting
AS $$
  # return tuple containing lists as composite types
  # all other combinations work also
  return ( [ how, "World" ], [ how, "PostgreSQL" ], [ how, "PL/Python" ] )
$$ LANGUAGE plpython3u;
</programlisting>
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>Iterator (any object providing <symbol>__iter__</symbol> and
      <symbol>__next__</symbol> methods)</term>
     <listitem>
      <para>
<programlisting>
CREATE FUNCTION greet (how text)
  RETURNS SETOF greeting
AS $$
  class producer:
    def __init__ (self, how, who):
      self.how = how
      self.who = who
      self.ndx = -1

    def __iter__ (self):
      return self

    def __next__(self):
      self.ndx += 1
      if self.ndx == len(self.who):
        raise StopIteration
      return ( self.how, self.who[self.ndx] )

  return producer(how, [ "World", "PostgreSQL", "PL/Python" ])
$$ LANGUAGE plpython3u;
</programlisting>
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>Generator (<literal>yield</literal>)</term>
     <listitem>
      <para>
<programlisting>
CREATE FUNCTION greet (how text)
  RETURNS SETOF greeting
AS $$
  for who in [ "World", "PostgreSQL", "PL/Python" ]:
    yield ( how, who )
$$ LANGUAGE plpython3u;
</programlisting>

      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

   <para>
    Set-returning functions with <literal>OUT</literal> parameters
    (using <literal>RETURNS SETOF record</literal>) are also
    supported.  For example:
<programlisting>
CREATE FUNCTION multiout_simple_setof(n integer, OUT integer, OUT integer) RETURNS SETOF record AS $$
return [(1, 2)] * n
$$ LANGUAGE plpython3u;

SELECT * FROM multiout_simple_setof(3);
</programlisting>
   </para>
  </sect2>
 </sect1>

 <sect1 id="plpython-sharing">
  <title>Sharing Data</title>
  <para>
   The global dictionary <varname>SD</varname> is available to store
   private data between repeated calls to the same function.
   The global dictionary <varname>GD</varname> is public data,
   that is available to all Python functions within a session;  use with
   care.<indexterm><primary>global data</primary>